problem installing apps

I did a search but couldn't find anything on this issue...perhaps I'm searching for the wrong terms. I'm hoping someone out there can help me solve the case of the missing apps....

I recently hard reset my 650 and am reinstalling old apps (clean installs, one by one) and installing some new apps to try out. Most of them have installed fine, but I had problems last night with two apps that I've never installed before.

I was using the Palm Desktop Quick Install tool (just double-clicking on the .prc files), and the sync went through without an error. However, the apps didn't show up at all in any of the menus on the Treo. I am not using a third-party launcher...just using the regular Palm OS interface. The apps didn't show up in any category (including "Unfiled" and "All"), and they also didn't show up when I selected "Category" in the "App" menu. However, if I selected "Info" or "Delete," the apps did show up in those menus, complete with version numbers. I deleted the apps and tried reinstalling a few times, but the problem never resolved -- I could never see the apps in the menu, so of course I couldn't launch them.